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The Single UNIX &reg; Specification, Version 2<br>
Copyright &copy; 1997 The Open Group

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<h4><a name = "tag_000_008_225">&nbsp;</a>NAME</h4><blockquote>
sched_setscheduler - set scheduling policy and parameters
(<b>REALTIME</b>)
</blockquote><h4><a name = "tag_000_008_226">&nbsp;</a>SYNOPSIS</h4><blockquote>
<pre><code>

#include &lt;<a href="sched.h.html">sched.h</a>&gt;

int sched_setscheduler(pid_t <i>pid</i>, int <i>policy</i>,
    const struct sched_param *<i>param</i>);
</code>
</pre>
</blockquote><h4><a name = "tag_000_008_227">&nbsp;</a>DESCRIPTION</h4><blockquote>
The
<i>sched_setscheduler()</i>
function sets the scheduling policy and scheduling parameters of
the process specified by
<i>pid</i>
to
<i>policy</i>
and the parameters specified in the
<b>sched_param</b>
structure pointed to by
<i>param</i>,
respectively.
The value of the
<i>sched_priority</i>
member in the
<b>sched_param</b>
structure is any integer within the inclusive priority range
for the scheduling policy specified by
<i>policy</i>.
If the value of
<i>pid</i>
is negative, the behaviour of the
<i>sched_setscheduler()</i>
function is unspecified.
<p>
The possible values for the
<i>policy</i>
parameter are defined in the header file
<i><a href="sched.h.html">&lt;sched.h&gt;</a></i>.
<p>
If a process specified by
<i>pid</i>
exists and if the calling process has permission,
the scheduling policy and scheduling parameters will be set for the
process whose process ID is equal to
<i>pid</i>.
<p>
If
<i>pid</i>
is zero, the scheduling policy and scheduling parameters will be set
for the calling process.
<p>
The conditions under which one process has the appropriate privilege
to change the scheduling parameters of another process
are implementation-dependent.
<p>
Implementations may require that
the requesting process have permission
to set its own scheduling parameters or those of another process.
Additionally, implementation-dependent restrictions may apply
as to the appropriate privileges
required to set a process's own scheduling policy, or another
process's scheduling policy, to a particular value.
<p>
The
<i>sched_setscheduler()</i>
function is considered successful if it succeeds
in setting the scheduling policy and scheduling parameters of the process
specified by
<i>pid</i>
to the values specified by
<i>policy</i>
and the structure pointed to by
<i>param</i>,
respectively.
<p>
The effect of this function on individual threads is dependent on the
scheduling contention scope of the threads:
<ul>
<p>
<li>
For threads with system scheduling contention scope, these functions
have no effect on their scheduling.
<p>
<li>
For threads with process scheduling contention scope,
&nbsp;the threads' scheduling policy and associated parameters
will not be affected.
However,
the scheduling of these threads with respect to threads in
other processes may be dependent on the scheduling parameters of their
process, which are governed using these functions.
<p>
</ul>
<p>
If an implementation supports a two-level scheduling model in which
library threads are multiplexed on top of several kernel scheduled
entities, then the underlying kernel scheduled entities for the system
contention scope threads will not be affected by these functions.
<p>
The underlying kernel scheduled entities for the process contention
scope threads will have their scheduling
policy and associated scheduling parameters
changed to the values specified in <i>policy</i> and <i>param</i>, 
respectively.
Kernel scheduled entities for use by process contention scope
threads that are created after this call completes
inherit their scheduling policy and associated
scheduling parameters from the process.
<p>
This function is not atomic with respect to other threads in the
process.
Threads are allowed to continue to execute
while this function call is in the process of changing the scheduling 
policy and associated scheduling parameters for the underlying kernel 
scheduled entities used by the process contention scope threads.
</blockquote><h4><a name = "tag_000_008_228">&nbsp;</a>RETURN VALUE</h4><blockquote>
Upon successful completion, the function returns the former
scheduling policy of the specified process.
If the
<i>sched_setscheduler()</i>
function fails to complete successfully,
the policy and scheduling paramenters remain unchanged, and
the function returns a value of -1 and sets
<i>errno</i>
to indicate the error.
</blockquote><h4><a name = "tag_000_008_229">&nbsp;</a>ERRORS</h4><blockquote>
The 
<i>sched_setscheduler()</i>
function will fail if:
<dl compact>

<dt>[EINVAL]<dd>
The value of the
<i>policy</i>
parameter is invalid, or one or more of the parameters contained in
<i>param</i>
is outside the valid range for the specified scheduling policy.

<dt>[ENOSYS]<dd>
The function
<i>sched_setscheduler()</i>
is not supported by this implementation.

<dt>[EPERM]<dd>
The requesting process does not have permission
to set either or both of the scheduling parameters or
the scheduling policy of the specified process.

<dt>[ESRCH]<dd>
No process can be found corresponding to that specified by
<i>pid</i>.

</dl>
</blockquote><h4><a name = "tag_000_008_230">&nbsp;</a>EXAMPLES</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_008_231">&nbsp;</a>APPLICATION USAGE</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_008_232">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_008_233">&nbsp;</a>SEE ALSO</h4><blockquote>
<i><a href="sched_getparam.html">sched_getparam()</a></i>,
<i><a href="sched_getscheduler.html">sched_getscheduler()</a></i>,
<i><a href="sched_setparam.html">sched_setparam()</a></i>,
<i><a href="sched.h.html">&lt;sched.h&gt;</a></i>.
</blockquote><h4>DERIVATION</h4><blockquote>
Derived from the POSIX Realtime Extension (1003.1b-1993/1003.1i-1995)
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Copyright &copy; 1997 The Open Group
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